Cytogenetics Flashcards
Chromatin
During interphase
Euchromatin
Heterochromatin
Chromosome composition
Long arm (q) Short arm (p) Centromere Secondary constriction Satellite (role in nucleolus formation) Telomeres
Position of centromere
Metacentric
Submetacentric
Acrocentric
Telocentric
Cytogenetics
Study of chromosome structure, number &its mutations
Mutation cause during meiosis
Incorrect chromosome separation (# change)
Chromosome breaking & wrong joining (structure change)
Mutations results
Spontaneous abortion Anomaly of growth Disorder of organ development Disorder of reproduction, that can lead to sterility Disorder of immunity development Mental retardation
Material for examination of chromosomes
Cells grown in vitroto increase number (fytohemaglutinin)
Mitosis stopped after 2-3 days in metaphase by mitotic inhibitor colchicine
Cells are lysed in hypotonic solution to release chromosomes
Chromosomes are stained, photographed & grouped
Fytohemaglutinin
Stimulates mitosis
Colchicine
Prevents mitotic spindle forming
Karyology
Study of whole sets of chromosomes - chromosomal aberrations & sex
Karyotype
Observed chromosome characteristics of individual or species
Karyogram, Idiogram
Format of chromosomes arranged in pairs, ordered by size & position of centromere
Methods of identification of chromosomes
Chromosome banding
FISH
multiplex FISH
Chromosome banding
G-banding
R-banding
G banding
Treatment of chromosome in metaphase stage with trypsin & stain them with Giemsa
Trypsin
Partially digest protein
Giemsa
Dark bands are A,T rich, gene poor
R-banding
Reverse to G-bands
FISH
Use of highly specific DNA proves which are hybridised to interphase or metaphase chromosomes
DNA probe + FISH method
Labeled with fluorescent or non fluroescent molecules which are then detected by fluorescent antiboides
Probes bind to a specific region on target chromosome
Chromosomes are stained using contrasting color & cells are viewed using fluorescence microscope
multiplex FISH
More differently colored DNA probes
Mutation
Change in genotype, that can be inherited
Spontaneous mutation
By mistake in DNA replication & reparation mechanism
Induced mutation
Induced by mutagens
Types of mutations
1) Genome mutation (numerical a.)
2) Chromosomal mutation (structural a.)
3) Gene mutation
Genome mutation
Change in chromosome number
Aneuploidy
Euploidy
Aneploidy
Change of number of individual chromosome
Can lead to syndroms
Caused by nondisjunction of chromosomes in meiosis
Euploidy
Change of chromosome sets
Chromosomal mutation
Change in structure of chromosome
Gene mutation
Change in genes, nucleotides or their order
Down syndrome
Trisomy-21
Edwards syndrome
Trisomy-18
Patau syndrome
Trisomy-13
Turner syndrome
Monosomy of chromosome X
FEMALES
Klinefelter syndrome
Extra chromosome X
MALES
Metamale (Jacob syndrome)
Extra chromosome Y
MALES
Metafemale
Extra chromosome X
FEMALES
Deletion
Part of chromosome is deleted
Interstitial deletion
Inside of chromosome